1. Field of the Invention
The present invention relates to a package for accommodating a radio frequency circuit.
2. Description of the Related Art
Miniaturization is among the requirements of a package accommodating a radio frequency circuit. For package miniaturization, various functions (or circuit elements) may be integrated in an identical package. In this case, however, unwanted radiation occurring in the package produces interference between the signals of the respective functions, with the problem of adverse effects on the characteristics of the entire radio frequency circuit.
As a measure against this, Japanese Patent Laid-Open Publication No. 2000-307305 discloses a technology in which a periodic structure consisting of periodically-altered materials is arranged on an inner wall of a package containing a radio frequency circuit. The radiation energy from unwanted radiation sources in the package is thus confined locally to prevent interference with other devices (first conventional technology). The foregoing publication also discloses a second conventional technology in which partitions are arranged in the package with respect to each of the functions of the radio frequency circuit.
Now, in terms of package size, the second conventional technology requires some space between the partitions and the radio frequency circuit in order to avoid interaction between the partitions and the circuit. This means a limit to minimization. Meanwhile, the first conventional technology uses no partition and thus dispenses with the space layout for partitions accordingly.
Nevertheless, the foregoing first conventional technology has not taken account of the miniaturization associated with the distance between the periodic structural inner walls of the package and the radio frequency circuit. More specifically, when the periodic structure is put near the radio frequency circuit which is formed as a planar circuit, it is unknown how the planar circuit itself is characteristically affected.